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Johannes Kepler Mars’ orbit is not a perfect circle, it is elliptical The speed of Mars’ orbit changes Closer to sun = faster Farther away from sun = slower Lead to Kepler’s 3 Laws

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Kepler’s 1 st Law The path of each planet around the sun is an ellipse with the sun at one focus

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Kepler’s 2 nd Law Each planet revolves so that the “imaginary line” that connects it to the sun sweeps equal amount of area in equal time intervals Closer to sun = faster Farther away = slower

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Kepler’s 3 rd Law The square of a planet’s orbital period is proportional to the cube of its distance from the sun Orbital period - how long it takes to orbit the sun Astronomical Unit (AU) – average distance between Earth and sun – 150 million km T 2 = d 3 ; T = orbital period, d=distance from sun in AUs

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Kepler’s Laws Tri-fold Use a tri-fold/brochure to explain Kepler’s 3 Laws. There should be no words other than labeling each 3 rd as to which law you are demonstrating. You may also use the formula for Kepler’s 3 rd law.

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Orbits Barycenter – point between two objects where they balance each other When a moon orbits planet, or planet orbits a star, both bodies are orbiting around a point that lies outside of the larger body (star/planet) http://en.wikipedia.org/wiki/Barycentric_coor dinates_(astronomy) http://www.youtube.com/watch?v=KnHUAc2 0WEU http://www.youtube.com/watch?v=rKo6tfFtZ g8 (2:59)

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Orbits The Sun is NOT a stationary object. Sun moves as the planets tug on it Sun orbits the solar system’s barycenter

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Moon and Earth Relationship Earth pulls on the moon, and moon pulls on Earth This “tugging” from the moon can cause the Earth to bulge

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Moon and Earth Relationship Earth’s solids cannot give, however water does, causing our tides Two high tides and two low tides a day 12hrs and 25 min between two high tides

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Moon and Earth Relationship Rise and fall daily due to Earth, Sun, and Moon interactions Since earth is rotating, we experience two tides each day

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Moon and Earth Relationship Spring Tides – when moon and sun interact together and form extreme tides. Occurs during full and new moons